Variable resistor with switch



June 18, 1968 B. H. MATTHEWS ET Al. 3,389,365

VARIABLE RESISTOR WITH SWITCH Filed Aug. v23, 1965 3 Sheets-Sheet 1 .VV'\""\T Haj? H PMU- June 18, 1968 B. H, MATTHEWS mL 3s965 VARIABLE RESISTOR WITH SWITCH Filed Aug. 23, 1965 3 Sheets-Sheet 2 E7- g/.iUf- Tf1-gil June 18, 1968 B. H. MATTHEWS ET Al. 3,389,365

VARIABLE RESISTOR WITH SWITCH Filed Aug. 23, 1965 3 Sheets-Sheet 3 N11/'IUI'. 12A] 5 v United States Patent O "ice 3,389,365 VARIABLE RESISTOR WITH SWITCH Benjamin H. Matthews, Peninsula, and Jules W. Rhine, Bedford, Ohio, assignors to Lucerne Products, Inc., Northfield, Ohio, a corporation of Ohio Filed Aug. 23, 1965, Ser. No. 481,564 7 Claims. (Cl. SSS-200) ABSTRACT F THE DISCLOSURE A combination electric switch and resistor speed control is used to regulate the speed of a power tool. An activating trigger is slidable on an insulative base for switching a resistor in circuit with the tool motor and selectively decreasing the amount of resistance in circuit as the trigger is depressed. The resistance element and switching contacts are located on a support fixed to the base and a wiper means is slidably received bythe support and positioned to'be -moved with the trigger. Alternatively, the resistance element and switching contacts are fixed to a surface of the trigger and the wiper means is fixed to the support.

This invention relates to electrical switch apparatus which has a movable switch contact assembly that includes a slidable bridging switch contact operable between bridging and non-bridging positions to connect and disconnect respectively, a source of electrical energy to a circuit input, and a second contact assembly which includes a rheostat assembly having a slidably actuated rheostat element operable to adjust said rheostat and regulate the magn-itude of electrical energy to said circuit input.

It is therefore one of the objects of the present invention to provide electrical switch apparatus of the type above defined, and further which can be miniaturized in its structure so that it can be readily inserted into the housing of a portable tool such as an electric drill, saw or the like and which may be operable by the conventional finger actuated trigger of said tool to control the speed of the drive motor of said tool.

Additional objects and advantages of the electrical switch apparatus ofthe present invention will be apparent to one skilled in the art to which it pertains and upon reference to several preferred embodiments thereof as are described herein and illustrated in the accompanying drawings wherein:

FIG. 1 is a side view of the electrical switch apparatus of the present invention disposed in its operative position within the handle of a portable electric tool or the like;

FIG. 2 is an end view looking in the direction generally indicated by the arrows 2`2 shown in FIG. l;

FIG. 3 is a plan view of the electrical switch apparatus removed from its tool housing;

FIG. 4 is a plan view taken approximately on the line 4--4 shown in FIG. l;

FIG. 5 is a sectional view taken approximately on the plane as indicated by the lines 5-5 shown in FIG. l;

FIG. 6 is a sectional view taken approximately on the line 6-6, as shown in FIG. l;

FIG. 7 is a schematic wiring diagram of a typical electrical control circuit of an electrical portable tool or the like and incorporating the switch apparatus of the present invention;

FIG. 8 is a longitudinal sectional view taken approximately on the line 8 8 shown in FIG. 2;

FIG. 9 4is a similar longitudinal section taken on line 9 9 of FIG. 2;

FIG. -10 is a longitudinal sectional view similar to FIG. 8 but with the movable rheostat actuating element shown Patented June 18, 1968 in an intermediate position with respect to the fixed or stationary rheostat element;

FIG. l1 is a longitudinal sectional view similar to FIG. 9 and showing the electrical switch bridging member in a first bridging position with respect to the fixed or stationary switch contacts ant occurring at the instant the rheostat actuating element is moved to the FIG. 10 position;

FIGS. l2 and 13 are longitudinal sectional views similar respectively to FIGS. 10 and 1l, but with the rheostat actuating element and bridging switch contact of the movable contact assembly in their fully actuated position;

FIG. 14 is a fragmentary perspective view of the rheostat assembly;

FIG. 15 is a plan View of a second embodiment of switch housing assembly and showing the stationary or ixed switch and rheostat elements of said assembly;

FIG. 16 is a plan view of the movable switch contact assembly incorporated in the second embodiment of switch apparatus of the present invention;

FIG. 17 is a longitudinal sectional view of the modified rheostat assembly shown in its off position;

FIG. 18 is a view similar to FIG. 17 but with the movable rheostat element moved to an intermediate position; and

FIG. 19 is a view also similar to FIG. 17 but with the movable rheostat element moved to its full on position.

The electrical switch apparatus as herein disclosed is especially designed to be utilized with a motor control circuit or varying the speed of an electrical seriesmotor of the type used in a portable electrical tool such as a drill, saw or the like and is operable to provide a variable magnitude of electrical energy to said motor.

Referring momentarily to FIG. 7, a typical motor control circuit is schematically illustrated and shows a series motor with its armature and field connected in series with each other and across line conductors L1 and L2 to which is applied a source of alternating current voltage such as v. A.C.

The electrical switch apparatus of the present invention as shown in its entirety at S is connected in series in either line L1 or L2. For purposes of identification the switch assembly is provided with a pair of output leads L3, L4 which connect respectively to line conductor L1 and to one side of the motorarmature.

Likewise, as will be hereinafter more clearly described, the switch assembly is of such electrical configuration as to be incorporated into a plurality of motor control circuits. For example, as shown in FIG. 7 herein the bridging contact 33 may be connected to the movable rheostat element 62 by connecting terminal points A1 and A2 together to enable the instant switch assembly to be used in the FIG. 7 configuration of motor control circuit. Likewise, by connecting terminal points A1 and A2 together in the manner shown in FIG. 7 the movable bridging contact 42 is also connected serially into the circuit etective to control the application of electrical energy to said circuit and motor. Likewise, for use of the instant switch assembly in a motor control circuit of the type that is disclosed in copending application Ser. No. 354,957, the terminal points A1 and A2 are connected respectively to the base c of the SCR 15 and to the conductor 22 of the circuit disclosed therein. As will be also obvious hereinafter, the electrical switch apparatus may be readily applicable to other configurations of motor control circuitry not herein specifically referred to.

With reference now directed to FIG. l, the electrical switch apparatus of the present invention, as identified at 10, is sufficiently miniaturized so as to enable the same to be readily inserted into the housing of a portable hand tool 11 such as Ian electric drill, saw or the like, said apparatus having a somewhat rectangular housing i12 formed preferably of a plastic material or the like in which the switch elements are disposed. The housing |12 is seen to be suitably mounted in the handle part 11a of the tool housing, the usual trigger 13 extending outwardly therefrom and actuata-ble by the finger of the operator in the normal manner. By squeezing the trigger 13, the movable actuator 15 of the switch apparatus is slidably actuated as will be hereinafter described so as to connect and vary simultaneously the magnitude of electrical energy to the tool motor effective to vary its speed.

One embodiment of switch apparatus of the present invention is illustrated in FIGS. 1 6 and 8-14 and is seen to include the aforementioned housing 12 of rectangular configuration upon which is slidably mounted the movable actuator l15 which is in the form of a bar and which may be preferably integrally formed with the aforementioned tool trigger 13.

As best seen in FIG. 1, the slide bar 15 is mounted on top of the housing I12, being secured to the latter as to be reversibly slidably movable longitudinally thereover by an inverted U-shaped clamp 17 which as seen in FIG. 2 has inwardly opposed fingers 19 provided at the ends thereof and which engage the switch housing 12 at recesses 20 located at the ends thereof being thus effective to securely fasten said slide bar 15 thereto.

As seen in FIG. 8, the housing 12 is of rectangular configuration having upstanding end and side walls 22 and 23 respectively, preferably integrally formed with the housing base 24 to thereby define an open-ended boxshaped container having a chamber 25 of similar configuration formed therein.

A switch plate identified at 30 is disposed within the upper open end of the housing 12 being preferably slightly smaller in its dimensions so as to substantially completely close the housing chamber 25. The switch plate 30, as best seen in FIG. 5, has a set of fixed or stationary switch contacts 32, 33 and 34 mounted on its upper surface 30a which are secured t said plate in longitudinally spaced relation to each other. Spaced laterally therefrom a narrow elongated rheostat bar as identified at 36 is mounted on its one longitudinal edge on said plate and extends longitudinally therealong in parallel spaced relation to said contacts.

As seen in FIGS. and 9, the set of switch contacts 32, 33 and 34 project upwardly above the surface 30a of the switch plate 30, fixed contact 32 having a rectangular fiat portion as indicated at 32a and an upwardly projecting nipple-shaped camming portion 32b integrally formed on its end closely adjacent to contact 33. Switch contacts 33 and 34 in turn are each preferably circular in configuration.

As seen in FIGS. 5, 8 and 14, the upright rheostat bar 36 is composed of a suitable non-conducting base, as indicated at 36a, such as bakelite and which is covered on its one side surface with two carbon tracks 37a and 37b forming a preselected value of resistance for example on the order of 100,000 ohms, the value depending upon the value of the components in the motor circuit to which it is connected. Track 37b on the inner end thereof connects to an intermediate metallic conductor plate 38. The opposite or remote end of the carbon track 37a is seen to connect with a similar metallic conductor plate 39. As best seen in FIGS. and 14, the carbon track 37a is terminated at its inner end at 37e to space said track from the conductor plate 38.

The slide bar 15, which is slidably mounted on top of the switch housing 12, carries a pair of contacts which are movable therewith into selective engagement with the stationary contacts 32, 33, 34 and the rheostat bar 36.

As ibest seen in FIG. 9, the slide bar is formed with a recess as indicated at 40 into which is disposed a metallic contact 42 being somewhat of inverted U-shaped configuration, coil spring 43 being disposed in blind hole 45 formed in said bar 11'5 and effective to bias said contact 42 toward the switch plate 30.

Referring now to FIGS. 9, 11, and 13, by pressing the trigger 13 the slide bar 15 is slidable over the housing 12 from left to right causing the contact 42 to move from its FIG. 9 position thence to a plurality of intermediate positions as represented in its FIG. 11 position and finally to its FIG. 13 position.

As shown in FIG. 9, the contact 42 has a contacting end portion thereof as shown Vat 42a which, in the FIG. 9 or off position of the switch assembly has its bottom edge riding upon the top of the camming portion 32b of the fixed contact 32, being urged into contact therewith by the coil spring 43.

Said end portion 42a is formed with an angular wall 42c which extends outwardly and rearwardly therefrom to terminate with the main stem portion`of the body of the contact 42.

The Iangular wall 42e of said movable contact 42 and the upwardly extending camming portion 32a of contact 32 are each of such related configuration that as the switch bar 15 is moved from its FIG. 9 position toward its FIG. 11 position, said contact 42 is cammed so that its forward contact portion 42a is dropped directly onto the fixed contact 33 prior to and without any initial wiping action occurring between the said contacts 42 and 33.

With the slide bar -15 moved toward its FIG. 1l position contacts 32 and 33 are connected to each other by movable contact 42, said switch elements thus defining a closed contact or switch position for said assembly.

The closing of switch contacts 32, 33 by contact 42 is shown schematically in FIG. 7 to connect line conductor L to the switch apparatus S, and with the conductors A1 and A2 connected together, said line conductor L1 is also connected to the adjustable element of the rheostat.

Thereafter, with the trigger 13 ibeing additionally moved to the right to its FIG. 13 position, the contact 42 is moved therewith, its tail portion sliding along the rectangular fiat section 32a of the contact 32, whereupon its forward portion 42a rides over and partially onto the top of contact 34 thus bridging said contacts 33, 34 and connecting the same with contact 32.

The contacts 33, 34 being connected to each other and to the contact 32 by movable contact 42 is also shown schematically in FIG. 7 to connect line conductor L1 directly to the armature of the motor thus bypassing the rheostat assembly.

With reference directed now to FIGS. 8, I10 and 12, the slide bar 15 is also formed with a second rectangularshaped recess 60 which is spaced laterally from the recess 40. A contact 62 is disposed in said recess 60 and is formed of a suitable conductive material and has a plurality of depending fingers 63-67 disposed as best seen in FIG. 14 in longitudinal spaced relation along and projecting outwardly from the base of said contact.

The contact 62 is intended to engage the rheostat bar 36 being slidably actuated therealong so as to connect predetermined portions of the carbon tracks 37a and 37b thereof to the energy source being thereby operable as a variable resistance connected in series with the line conductor L1 effective to vary the magnitude of electrical energy delivered to the connected motor.

As seen in FIG. 14, the contact 62 is mounted on the top longitudinal edge 36a of the rheostat bar 36 whereby the end fingers 63 and 67 extend over and engage the carbon tracks 37b and 37a respectively, the centrally disposed finger 65 extending over and engaging the opposite side surface of said rheostat bar, the material forming said contact 62 being preferably resilient in characteristic whereby said engaging fingers act to resiliently hold the contact 62 thereon.

To provide additional stability to the movable contact 62 as it slides along the upper edge 36a of the bar 36, the intermediate fingers 64, 66 of said contact are seen to be shorter in their respective length so as to slidably engage the upper edge 36a of said bar.

As best seen in FIGS. 8 and 9, a connector bar 68 extends transversely across the underside of switch plate 30 and connects contact 34 and conductor plate 39 together.

With the slide bar 15 disposed in its FIG. 8 position corresponding to the olf position for said switch the contact fingers 63 and 67 are in engagement with the carbon tracks 37a and 37b whereby a predetermined maximum value of resistance of said rheostat is connected serially in circuit with the terminal point A2 and line conductor L4. f

As the slide bar 15 is thereafter moved to the right by pressing upon the trigger 13 the contact 62 is slidably moved along the carbon tracks 37a and 37b simultaneously with the movement of bridging contact 4Z. As the slide bar 15 is moved to the right progressively toward its FIG. and l2 positions, the value of the rheostat resistance is likewise progressively reduced until said slide bar is moved to its FIG. 12 position at which the contact fingers 63 and 67 engage the conductor plates 38 and 39 respectively, thus, connecting contacts 62 directly across the terminal point A2 and line conductor L4 to thereby short out the carbon tracks 37b, 37a whereby line conductor L1 of the motor circuit may be connected directly to the one side of the motor armature.

At this instant, as is aforementioned and as seen in FIG. 13, the trailing end of bridging contact 42 is in engagement with the fixed contact 32 and its opposite end is in engagement with both contacts 33 and 34 thereby connecting the line conductor L1 through closed switch contacts 42, 34 to conductor L4 and to said one side of the motor armature to provide a second conductor path to said armature.

Upon the operator releasing the trigger 13, the coil spring 75 interposed between the slide bar 15k and the end wall 17a of the bracket 17 as seen in FIG. 9 is operative to spring said bar and trigger to its off position as shown in FIGS. 8 and 9. The instant switch apparatus is therefore seen to provide a first bridging switch assembly 32, 33, 34 and 42 which is operable to connect and disconnect respectively a source of electrical energy L1 to a circuit input (motor circuit) and a second variable rheostat assembly operable to vary the magnitude of electrical energy to said circuit input.

Further, in the instant switch assembly the actuation of the bridging switch (movable contact 42) and rheostat (rheostat contact 62) are carried by the slide bar 15 and slidably actuated simultaneously. f

In FIGS. -19 a second embodiment of switch apparatus of the present yinvention is herein disclosed, and differs from the previous switch structurek in the rheostat assembly.

With reference directed particularly to FIGS. 15 and 17, the switch plate 30 has the fixed or stationary contacts 32, 33 and 34 mounted therein and which function with the bridging or movable switch contact 42 in the same manner as in the previous switch assembly.

The modified rheostat assembly comprises a pair of metallic spring-like fingers 80, 81 securely fastened at one end to the switch plate 30 in longitudinal spaced relation to each other and extending angularly upwardly therefrom. Finger 80 is connected to one end of conductor A2 and linger 81 is attached to bracket 68 to which is connected one end of conductor L4.

As in the previous switch assembly, when using the switch apparatus in the motor control circuit as shown in FIG. 7, conductors A1 and A2 are connected together to thereby connect the stationary contact 33, the movable bridging contact 42 and finger 80 to each other.

Likewise, when using the switch apparatus in conjunction with the motor control circuit of the type disclosed in the aforesaid copending application Ser. No. 354,957 the conductors A1 and A2 are connected to fixed contact point d and to conductor 22, respectively.

The slide bar 15 is formed with a recess 85 spaced laterally from the recess 40 and extending generally longitudinally along said bar in parallel spaced relation to said recess 40. f

A rheostat bar 87 is disposed in the recess 85, being secured by any suitable means such as adhesive to the top wall 89 thereof.

As seen in FIG. 16, the underside of the rheostat bar 87 is provided with a somewhat L-shaped copper bus bar 91 which is disposed adjacent a somewhat similarly shaped carbon track 92 the surfaces of said bus bar and carbon track being preferably coplanar.

A at spacer member 95 is seen to have a pair of slots 97 and 98 formed on opposite ends and adjacent the opposed longitudinal edges thereof and into which the curved ends of the fingers 80 and 81 are disposed.

The spacer member 95 is preferably of such Width as to enable it to be inserted into the recess 85 and freely movable therethrough.

With the slide bar 15 mounted over the switch plate 30', the fingers 80 and 81 project upwardly into recess 85 and are pressed against the rheostat bar 87.

As seen in FIGS.V16 and 17, with the slide bar 15 and trigger 13 in the off position for the switch apparatus, the curved end of finger 80 is intended to engage the carbon track 92 at approximately point a `and in like manner at point b by finger 81. At this switch position the resistance of the carbon track 92 between points a and b represents the rheostat resistance connected between line conductors L3 and L4 in the motor control circuit shown in FIG. 7.

With the trigger 13 further depressed to a position such as illustrated in FIG. 18, whereby the fingers 80 and 81 engage the carbon track 92 at points a and b' respectively the resistance between said points a' and b' has been progressively reduced to thereby provide a larger magnitude of electrical energy to the motor effective to increase the speed thereof to, for example, half speed.

As the trigger 13 is moved to its FIG. 19 position, the fingers 80 and 81 engage the copper -bus par 91 at points x and y respectively, whereby the rheostat resistance is f zero and maximum energy is available to the motor to enable the same to attain full speed.

Having thus described several preferred embodiments of switch apparatus of the present invention it will be realized that the same is susceptible to various modifications, combinations and arrangements of parts thereof without departing from the inventive concepts as are defined in the claims.

What is claimed is:

1. In an electric switch, in combination, a switch base, at least a pair of lstationary contacts mounted on said :base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact 'and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement with at least one of said stationary contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising bar means supported on said -base and having a surface disposed generally perpendicular to said base, resistor means on said surface connected to conductive terminal means, la :second contact operatively connected to said actuator and having contacting means engageable with said resistor means, said second contact being movable with said actuator to selective positions along said resistor means to provide a plurality of resistance values between said terminal means, and said second contact being movable to a position to connect across said terminal means effective to provide a second conductive path through said second contact and between said terminal mean-s short-circuiting at least a part of said resistor means therebetween.

2. In an electric switch, in combination, a switch base, at least a pair of stationary contacts mounted on said base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement .with at least one of said stationary contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising a pair of conductive terminals spaced along said base, an elongate bar supported on said base having a surface disposed generally perpendicular to said base and extending longitudinally therealong in parallel spaced relation to said stationary contacts, a pair of resistor tracks carried on said surface and disposed in longitudinal spaced relation to each other, one of said terminals connecting with adjacent ends of said resistor tracks, the other of said terminals connecting with the opposite end of one of said resistor tracks, a second conductive contact operatively connected to said actuator and formed with at least two contact fingers each of which engages one of said resistor tracks, said second contact being slidably movable by said actuator along said lbar to move said contact lingers along said resistor tracks and provide a plurality of resistance values between said terminals, and said second contact being movable -by said actuator to bring said contact lingers into engagement wih said terminals effective to provide a second conductive path between said terminals and short-circuit at least a part of said resistor tracks therebetween.

3. In an electric switch, in combination, a switch base, at least a pair of stationary contacts mounted on said base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement with at least one of said stationary contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising a pair of terminals carried on said base, bar means supported on said base and having a sur- CTI face disposed generally perpendicular to said base, a pair of resistor elements mounted on said surface each connected to said terminals, a second contact operatively connected to said actuator and having contacting means engageable with each said resistor element, and said second contact being slidably movable with said actuator to selective positions along said resistor elements to provide a plurality of resistance values between said terminals.

4. In an electric switch as defined in claim 1 and wherein the conductive terminal means are spaced along said base of said switch, said bar means includes an elongate bar supported on said base which extends longitudinally therealong and having a surface disposed generally perpendicular to Vsaid base and said resistor means includes a pair of resistor tracks on said surface connecting to said terminal means, and wherein said second conductive contact includes a pair of fingers each engaging one of said resistor tracks, said second contact being slidably movable by said actuator along said ybar to slide said contact fingers along said resistor tracks and provide a plurality of resistance values between said terminal means.

5. A rheostat assembly as is defined in claim 4 and which includes at least one additional finger on said second contact engaging said elongate bar effective to stabilize said second contact on said bar.

6. A rheostat assembly as is defined in claim 1 and wherein the second contact is disposed in approximate parallel spaced relation to said bridging contact.

7. A rheostat assembly as is delined in claim 4 and wherein the elongate bar is spaced transversely from said stationary contacts and extends generally parallel therewith along said base.

References Cited UNITED STATES PATENTS 793,494 6/1905 Yates 338-162 2,678,985 5/1954 Smith 338-1Z8 2,999,991 9/1961 Bender 338-162 3,303,403 2/1967 Donanno 338-78 RICHARD M. WOOD, Primary Examiner.

I. G. SMITH, Assistant Examiner. 

